Blending effects of thermoplastic polyurethane based on polycaprolactone diol, PU (PCL diol), and poly (?-caprolactone) (PCL) on the rheological properties and morphological behavior of the solvent-cast blends were investigated by parallel plate rheometer. The amount of PCL was varied from 20 to 50% by weight. Fourier transform infrared (FTIR) results showed existence of hydrogen bonding in PU/PCL blends. From FTIR, we also found the increase of PCL composition tends to reduction of intermolecular hydrogen bonding and enhancing of microphase separation in blends. Differential scanning calorimetry (DSC) indicated that these blend systems are partially miscible. Based on rheological characterization, decrease can be seen in the moduli, zero shear viscosity and plateau modulus of blends, as compared with net PU. Using Cole-Cole plots and composition dependencies of ?0 and the other viscoelastic functions expressed variation of morphology of blends due to increase of PCL content. Frequency sweep tests on PU/PCL (80/20) at five temperatures showed validity of time-temperature superposition in this blend. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012